Your sister can take her to the local hospital ER that has an in-patient psychiatric program and ask for a mental health evaluation. Typically, involuntary admissions require a fairly high bar. She would need to be actively suicidal or homicidal. Voluntary admissions depend on bed availability and the severity of the situation. Just taking her to the ER will get you a psychiatric assessment officer that may help guild outpatient treatment. Your sister can also call the local adult protective services and open a case.

IANAL, ER physician that works in a psych intake hospital.

PS- For things like this it’s always best to show up in the ER early in the morning on a weekday and not 9pm Friday night.

I think involuntary admission is off the table. She's taking the long, slow approach to killing herself, rather than being actively suicidal. What would we say to adult protective services? She's not officially disabled, and she's only 62, so would she be in their remit?